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Motorcraft SP-542 plug superseded by SP-578? - NGK Ruthenium HX - New Plug Installation DIY


boostededge

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  • 2 months later...

Edited because I'm even more confused now. Using the NGK part finder is looks like OEM plugs were heat range 7? and the now NGK recommended plugs are heat range 6 wheras Ford is recommending a hotter plug heat range 8 possibly on SP-578? Going to that hot of a plug doesn't sound good, I can see why people would see less timing and be able to run less boost.

 

@1004ron you originally installed the LTR7BHX which are heat range 7 now your going to a COLDER plug LTR6BHX heat range 6.

 

Ford
SP-542 is heat range 7
SP-578 is heat range ?8?

 

Iridium
NGK ILTR7N8 is heat range 7 (original OEM equivalent)
NGK ILTR6S8 is heat range 6

 

Ruthenium
NGK LTR7BHX is heat range 7
NGK LTR6BHX is heat range 6
 

Edited by boostededge
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